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Tetrahedron 66 (2010) 1458–1464

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Tetrahedron

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A convenient synthesis of partially reduced benzo[c]phenanthrenes,its ketals and ketonesq

Ramendra Pratap a,d,*, Resmi Raghunandan b, Abhishek Kumar Mishra c, P.R. Maulik b,V.P. Gupta c, Vishnu Ji Ram a,d,*

a Medicinal and Process Chemistry Division, Central Drug Research Institute, Lucknow–226 001, Indiab Molecular & Structural Biology Division, Central Drug Research Institute, Lucknow–226 001, Indiac Department of Physics, Lucknow University, Lucknow-226007, Indiad Institut fur Organische Chemie Universitat des Saarlande, Saarbrucken-66123, Germany

a r t i c l e i n f o

Article history:Received 31 October 2009Received in revised form2 December 2009Accepted 7 December 2009Available online 6 January 2010

Keywords:Benzo[c]phenanthrene2-Oxo-4-(piperidin-1-yl)-5,6-dihydro-2H-benzo[h]-chromene-3-carbonitrilesRing transformation

q CDRI communication No. 7475* Corresponding authors. Tel.: þ49 163 1855773 (R.Pþ91 522 2623405 (V.J.R.).

E-mail addresses: ramendrapratap@gmail.com, vji

0040-4020/$ – see front matter � 2009 Published bydoi:10.1016/j.tet.2009.12.026

a b s t r a c t

A concise and convenient synthesis of various partially reduced 6-sec-amino-1,2,3,4,7,8-hexahydro-,6-sec-amino-1,2,7,8-tetrahydrobenzo[c]phenanthrene-5-carbonitriles, 6-sec-amino-3,4,7,8-tetrahydro-1H-benzo[c]phenanthrene-2-one-5-carbonitrile cycloalkene ketals, pendant with electron donor andacceptor substituents has been described through base catalyzed ring transformation of 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles by cyclohexanone, 2-cyclohexen-1-one,1,4-cyclohexanedione monocycloalkene ketals. The acid catalyzed deketalation of 6-sec-amino-3,4,7,8-tetrahydro-1H-benzo[c]phenanthrene-2-one-carbonitrile ketals led to yield 6-sec-amino-3,4,7,8-tetra-hydro-1H-benzo[c]phenanthrene-3-carbonitrile-2-ones in excellent yield. We also performed the X-raystudies of the molecules 3d and 6a to know the degree of non-planarity.

� 2009 Published by Elsevier Ltd.

O

OH OH

OH OH

I II III

Figure 1. Benzo[c]phenanthrene and their metabolites.

1. Introduction

Polycyclic aromatic hydrocarbons (PAHs) have received con-siderable attention because of their fascinating chemistry andunique physical properties due to highly twisted geometry possiblyowing to the over crowding of atoms or groups present in the fjordregion. In these molecules, induced strain is relieved by buckling ofaromatic ring and bending of bonds, assuming helical conforma-tion. The helicity of polycyclic aromatic hydrocarbons can be fur-ther increased through bulky substitution in the fjord region as wellas through partial reduction or in combination. There is alsoa possibility for the reduced distortion if the twisting in the mol-ecule is unidirectional. Small helical molecules are of great signif-icance because of their rich chemistry,1 physical properties,2

technological and industrial applications.1 These molecules haveinherent chirality due to their twisted skeletons and racemize byinversion and exhibit chirotopic properties, if resolved. The pureenantiomers are useful as chiral auxiliaries for chiral induction andas shift reagents in NMR spectroscopy.3

.); tel.: þ91 522 2612411; fax:

ram@yahoo.com (R. Pratap).

Elsevier Ltd.

The high prevalence of various polycyclic aromatic hydrocar-bons in the environment and their threat to cause cancer in humanshas drawn substantial attention. In vivo these metabolize by thecombined action of enzymes P450 and epoxidehydrolase todiolepoxides that covalently bind to purine base of DNA throughC–N linkage to form stable adduct involving amino group ofdeoxyadenosine and deoxyguanosine. When repair enzymes do notexcise these lesions, mutation may occur upon DNA replication,resulting initiation of tumorigenesis. Benzo[c]phenanthrene (BcP, I)is relatively weak carcinogen4 present in the environment5 com-pared to benzo[a]pyrene. The 3,4-dihydrodiol (II) and the corre-sponding diolepoxide (III) derivatives of BcP are highly potentcarcinogenic metabolites (Fig. 1).6,7

One of the most intriguing problems in the study of carcinogenichydrocarbons is to establish the correlation between chemicalstructure and tumorigenic property. Various theories are proposed

OCOOMeNC

MeS SMe+

1. DMSO/KOH

2. EtOH/ O O

CN

1

HN

N

Scheme 1. Two steps synthesis of 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chro-mene-3-carbonitriles.

R. Pratap et al. / Tetrahedron 66 (2010) 1458–1464 1459

but none of them is satisfactory in all respect. Based on numerousexperimental facts, it has been concluded that partial reduction ofpolycyclic aromatic hydrocarbons reduces the carcinogenic prop-erty, possibly by disrupting the co-planarity of the molecule.6

Various approaches to the synthesis of benzo[c]phenanthrenering system are reported7,8 but none of them devoid from shortfallsof generality, multi-steps sequences with complex work-up andalso impractical for the construction of hindered and partially re-duced derivatives. The molecules of this ring system are synthe-sized in multiple steps through the Friedel–Crafts reaction of1-methallylsuccinic anhydride and benzene followed by reductionand cyclization.9 Further improvement in the synthetic strategyshorten the reaction steps and also improved the overall yields ofthe final products. Vilsmeier reaction of 1-(4-anisyl)-2-formyl-6-methoxy-3,4-dihydronaphthalene, which on cyclodehydration anddehydrogenation provided 3,10-dimethoxy-5-methyl-5,6,6a,7,8,12b-hexahydrobenzo[c]phenanthrene.10 A novel synthesis of ben-zo[c]phenanthrene and its 3,4-phenolic derivatives via the keyintermediate, 4-oxo-1,2,3,4-tetrahydrobenzo[c]phenanthrene hasbeen reported.11 It has also been obtained by alkylation of 1,3-cyclohexanedione by 2-(2-naphthyl)ethyl iodide, which aftercyclization and dehydrogenation gave 2-phenyl-4-hydroxy-benzo[c]phenanthrene.12 An efficient and convenient route forthe synthesis of benzo[c]phenanthrene through combined met-alation, Suzuki/Grignard cross coupling resimen13 has beenreported. An improved synthesis of benzo[c]phenanthrene-3,4-diol-1,2-epoxide has been achieved from 1-(2-naphthyl)-2-(2-methoxyphenyl)ethylene, via photocyclization in five steps in15% overall yield.14 Under a new strategy a cross coupling re-action of 2-bromo-5-methoxybenzaldehyde with naphthalene-1-boronic acid produced 2-(1-naphthyl)-5-methoxybenzaldehyde,followed by acid catalyzed cyclization with methanesulfonic acidafforded 3-methoxybenzo[c]phenanthrene.15 It has also beensynthesized15 by the photolysis of 2-naphthylstyrene, obtainedfrom the Wittig reaction of 2-naphthaldehyde and 2,5-dime-thylbenzyltriphenylphosphonium chloride. Generally, most ofthe reported procedures8c,9,13 for the construction of benzo[c]-phenanthrene derivatives suffer from the harsh reaction condi-tions and commercially non-availability of reagents.

The lack of simple and efficient route necessitated the de-velopment of an economical, efficient and regioselective synthesis ofpartially reduced benzo[c]phenanthrenes, their ketals and ketones.

2. Result and discussion

Herein, we report a facile and concise synthesis of functionalizedpartially reduced benzo[c]phenanthrenes through a base catalyzedring transformation of 2-oxo-4-sec-amino-5,6-dihydro-2H-ben-zo[h]chromene-3-carbonitriles with cyclohexanone, 2-cyclohexen-1-one, 1,4-cyclohexanedione monoethylene- and mono-2,20-dime-thyltrimethylene ketals separately in high yields. The presence ofelectron-withdrawing and donating substituents at position 3 and 4of benzo[h]chromene ring made it indispensable synthon for theconstruction of various polycyclic hydrocarbons. The syntheticpotential of 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles is enormous for generating molecular diversity.

The 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles, have been prepared in two steps. The first step of thereaction involves the synthesis of the 2-oxo-4-methylsulfanyl-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles16 by stirring a mix-ture of methyl 2-cyano-3,3-dimethylthioacrylate17 and 1-tetraloneusing powdered KOH as a base in DMSO at room temperature. This onamination with a secondary amine in ethanol at reflux temperatureproduced 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles in good yields16 and were used for the synthesis ofcongested diverse polycyclic aromatic hydrocarbons, Scheme 1.

As evident from the topography of 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles 1 that the C2, C4,and C10b positions are electrophilic in nature. However, the posi-tion C10b is more electrophilic compared to other positions due tothe presence of an electron-withdrawing CN substituent at position3 of the chromene ring and extended conjugation that made theposition highly prone to nucleophilic attack.

Various cyclic ketones and 1,4-hexanedione monocycloalkeneketals have been used as source of carbanions. The methylenegroup a- to carbonyl in the cyclic ketones is activated and formcarbanion in the presence of base. Thus, stirring an equimolarmixture of 1, cyclohexanone 2a and powdered KOH in DMF at roomtemperature for 2–3 h followed by usual work-up and purificationof crude product through column chromatography afforded 6-sec-amino-1,2,3,4,7,8-hexahydrobenzo[c]phenanthrene-5-carbonitriles3a–d in excellent yields (Scheme 2).

This reaction possibly proceeds through attack of a carbanion atposition C10b of 1 with Michael addition followed by ring closurewith loss of water and carbon dioxide to yield 3a–d (Scheme 2). Thepossibility for the formation of mechanistically obvious product 4was ruled out on the basis of reduced electrophilicity of the C4carbon due to the presence of amino group, which does not favorthe enolization of Michael adduct formed in the initial step.

Under analogous conditions, the reaction of 1 with 2-cyclo-hexen-1-one 2b followed the similar course of reaction to yieldpartially reduced benzo[c]phenanthrene-3-carbonitriles 3e–g ingood yields, Scheme 2.

A similar reaction of 1 with 1,4-cyclohexanedione was carriedout to obtain 6-sec-amino-3,4,7,8-tetrahydro-1H-benzo[c]phenan-threne-2-one-5-carbonitrile in single step but finally ended witha complex mixture, possibly due to the side reaction at other car-bonyl group. To avoid the complexity of reaction, synthetic strategywas changed by using their monoethylene- and 2,20-dimethyltri-methylene ketals as a source of carbanion. However, reaction of 1with 1,4-cyclohexanedione monoalkeneketal 5a and 5b separatelyproduced 6a–h in excellent yields, Scheme 3.

Attempts to cleave the cyclic ketal ring of 6e by amberlyst-15failed, but easily cleaved by stirring in formic acid at room tem-perature to yield 6-sec-amino-3,4,7,8-tetrahydro-1H-benzo[c]phe-nanthrene-2-ones 7 (Scheme 4).

In order to synthesize highly functionalized 7-helicenes, the ringtransformation of 1 was attempted by 7 under analogous reactionconditions, but only 7 was recovered. We tried several base andsolvent combinations as KOH/DMSO, NaH/THF, NaH/DMF, KOBut/DMF and K2CO3/DMF but failed to precede the reaction. We alsocarried out this reaction at elevated temperature but no positiveresult was achieved, possibly due to steric hindrance, which restrictsthe attack of carbanion generated in situ from 7 at C10b of the 1.

X-ray study of partially reduced benzo[c]phenanthrenes: The he-lical conformation in the benzo[c]phenanthrene has been observedowing to the distortion of aromatic ring in some way.8c Effect ofpartial reduction on acquiring helical conformation in partiallyreduced benzo[c]phenanthrenes is not explored due to non-availability of partially reduced benzo[c]phenanthrenes and is theconcern for present investigation.

6 Product Yield (%)

aCN

N

91

b CNN

CH3

94

c CNN

Ph

89

d CNN

N

Ph

81

e

CNN

94

fCN

N

CH3

89

gCN

N

Ph

91

hCN

N

O O

O O

O O

O O

O O

O O

O O

O O

92

CN

+O O

O

1 5 6

O O

CNN

N

O O

O O

O

O O

O

O O

O

=

Complex reactionmixture

O

O

a

b

cheme 3. Synthesis of cyclic ethylene ketal of 6-sec-amino-3,4,7,8-tetrahydro–1H-enzo[c]phenanthrene-2-one, cyclic trimethylene ketal of 6-sec-amino-3,4,7,8-tetra-ydro–1H-benzo[c]phenanthrene-2-one.

DMFKOH

O O

CN

+

O O

CN

O

O O

CN

OH

CN

OHH

CN

O

CN

X

O

1 2

3

4

N

N N

N

N

O O

2a = 2b =

3 Product Yield (%) 3 Product Yield (%)

a CN

N

89 e CN

N

79

b CN

N

CH3

92 f CN

N

CH3

84

c CN

N

Ph

87 gCN

N

N

Ph

87

dCN

N

N

Ph

95

Scheme 2. Probable mechanism for the synthesis of 6-sec-amino-1,2,3,4,7,8-hexahy-drobenzo[c]phenanthrene-5-carbonitriles (3a–d) and 6-sec-amino-1,2,7,8-tetrahy-drobenzo[c]phenanthrene-5-carbonitriles (3e–g).

R. Pratap et al. / Tetrahedron 66 (2010) 1458–14641460

For the study of conformational arrangements of the rings ofbenzo[c]phenanthrene, several substituted benzo[c]phenanthreneswere crystallized for X-ray structural analysis. Diffraction qualitycrystals of 6-(4-benzylpiperazin-1-yl)-1,2,3,4,7,8-hexahydrobenzo-[c]phenanthrene-5-carbonitrile 3d and 6-(piperidin-1-yl)-3,4,7,8-tetrahydro-1H-benzo[c]phenanthrene-2-one-5-carbonitrile-(2,20-dimethylene ketal) 6a were obtained in mixture of methanol inchloroform by slow evaporation at room temperature. The confor-mation of these compounds with arbitrary numbering is shown asORTEP diagram Figure 2, which indicates a non-planarconformation.

The least square plane calculation from X-ray crystallographicdata of 6a indicates that rings A and C are nearly planar. The averagemean plane angle for the twist between the rings A and C is 38.5�.The rings B and D adopt half chair conformation. The ring E adopts

Sbh

Figure 2. Displacement ellipsoid plot (30% probability) showing the molecular struc-ture of 3d and 6a with the atomic-labeling.

H.COOH/RT

7

6

CN

O O

H3C CH3

N

CNN

O

CN

O O

N

H.COOH/RT

6

X X X

7 X Yield (%)

a H 99b Benzyl 97

Scheme 4. Deprotection of cyclic trimethylene- and ethylene ketals.

Table 1Selected torsion and mean plane twist angles (�)

Comp. Atoms Torsion angles(�)

Mean plane angle(Twist angle �)

3d C4a-C5-C6-N2 �179.04 A, C 32.55C6-C5-C13-N1 �102.71C12-C12A-C12B-C12C 33.28C1-C12C-C12B-C12A 5.96C1-C12C-C4A-C5 174.05C12C-C12B-C6A-C7 173.92C12B-C12A-C8A-C9 175.52

6a C4a-C5-C6-N2 178.23 A, C 38.55C6-C5-C13-N1 �179.53C12-C12A-C12B-C12C �40.53C1-C12C-C12B-C12A �9.73C1-C12C-C4A-C5 �175.39C12C-C12B-C6A-C7 �164.43C12B-C12A-C8A-C9 �178.36

Table 2Selected bond lengths of 3d and 6a

Comp. Inner C–CBond lengths

Outer C–Cbond lengths

3d C1-C12C 1.522 C5-C6 1.391C12C-C12B 1.412 C6-C6A 1.381C12B-C12A 1.500 C6A-C7 1.513C12A-C12 1.394 C8-C8A 1.536

6a C1-C12C 1.518 C5-C6 1.392C12C-C12B 1.416 C6-C6A 1.397C12B-C12A 1.481 C6A-C7 1.515C12A-C12 1.403 C8-C8A 1.500

R. Pratap et al. / Tetrahedron 66 (2010) 1458–1464 1461

an envelope conformation while ring F adopts a full chair confor-mation. The distance between the non-bonded carbon atoms C1and C12 is 3 Å, which is shorter than any over crowded moleculeand from van der Waals radii of carbon atoms by 0.4 Å, which in-duces distortion in the molecule. This strain is relieved eitherthrough stretching and bending of the chemical bonds or bucklingof the aromatic rings.

Similarly the X-ray study of the compound 3d showed that theaverage mean plane angle for the twist between the rings A and C is32.5�. The distance between the non-bonded carbon atoms C1 andC12 is 2.994 Å. The torsion angles (C12-C12A-C12B-C12C and C1-C12C-C12B-C12A) of the compounds 6a are –40.5 and -9.7�, whilefor 3d are 33.28 and 5.9�. The torsion angles of benzo[c]phenan-threne and 1,4-dimethyl benzo[c]phenanthrene have 17.3 & 19.0and �29.3 & �18.4�, respectively. Some of the inner C–C bondlengths have been lengthened while the outer bonds are closer tothe normal single and double bond lengths. Thus, it is the ring B/C,that accommodates most of the torsional strain.

Here we showed the arrangement of molecules in the unit cell of3d and 6a. In case of 3d unit cell contain two molecule and in caseof 6a it contains 4 molecules in unit cell (Fig. 3).

Figure 3. Showing the arrangement of molecules in the unit cell.

The presence of spiro ring at C2 position in 6a enhances the de-gree of non-planarity in the compound and thereby induces helicity,by forcing the molecule to deviate from the most favorable planararrangement by bending out of the plane of the aromatic rings.

The contribution of spiro ring to the helical conformation in 6awas established by replacing it with hydrogen in 3d, which reducesthe repulsion and thereby torsion angles and degree of inducednon-planarity. Because of electronic repulsion between the tworings there is remarkable distortion in the case of 6a (w50�) ascompared to 3d (w39�)(Table 1 and 2).

3. Conclusions

We have developed an innovative and concise protocol for theconstruction of partially reduced highly functionalized benzo[c]-phenanthrenes through base catalyzed ring transformation of2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbon-itriles by different alicyclic ketones, using potassium hydroxide asa base and DMF as solvent at room temperature. A methodology forthe introduction of a carbonyl group at position 2 of the ben-zo[c]phenanthrene has also been developed using 1,4-cyclo-hexanedione mono ketal as an agent for the ring transformationfollowed by acid cleavage of the resulted ketal, providing 2-oxo-4-sec-amino-1,2,3,4,7,8-hexahydrobenzo[c]phenanthrene withoutusing any oxidizing agent and catalyst. The conformational studyfor the selected compounds by X-ray diffraction analysis has alsobeen done.

4. Experimental

4.1. General

All reactions were conducted in flame-dried glassware. Pre-coated Merck TLC plates were used for monitoring the reaction.Column chromatographic separation was performed on neutralalumina and silica gel (60–120 mesh). IR spectra were recorded ona Shimadzu 8201 PC FTIR Spectrophotometer. 1H NMR spectra wererecorded on Bruker DRX 200 as well as Bruker DRX 300 spec-trometer in deuterated solvents with TMS as internal reference.

R. Pratap et al. / Tetrahedron 66 (2010) 1458–14641462

Mass spectra were recorded on JEOL SX-102 (FAB) spectrometer.HRMS were recorded on JEOL JMS-600H (HRMS) spectrometer.Melting points were determined on Buchi-530 capillary meltingpoint apparatus and are uncorrected.

4.2. General procedure for the synthesis of 6-sec-amino-1,2,3,4,7,8-hexahydrobenzo[c]phenanthrenes (3a–d)

An equimolar mixture of 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles, cyclohexanone and KOH inDMF was stirred for 2–3 h. Completion of reaction was monitoredby TLC. Thereafter, reaction mixture was poured onto crushed icewith vigorous stirring followed by neutralization with 10% HCl. Theprecipitate obtained was filtered, washed with water, dried andpurified by neutral alumina column using 3% ethyl acetate in hex-ane as eluent.

4.2.1. 6-(Piperidin-1-yl)-1,2,3,4,7,8-hexahydrobenzo[c]phenan-threne-5-carbonitrile (3a). White powder; yield: 89%; mp: 156–158 �C; IR (KBr): 2926, 2855, 2368, 2213, 1596, 1461, 1351 cm�1; 1HNMR (300 MHz, CDCl3): d 1.62–1.70 (m, 8H, CH2), 1.84–1.93 (m, 2H,CH2), 2.63–2.67 (m, 2H, CH2), 2.73–2.77 (m, 2H, CH2), 2.93 (t,J¼5.97 Hz, 2H, CH2), 3.01 (t, J¼6.80 Hz, 2H, CH2), 3.21 (br s, 4H, CH2),7.21–7.30 (m, 3H, ArH), 7.55–7.59 (m, 1H, ArH); 13C NMR (75 MHz,CDCl3): d 21.16, 22.01, 22.99, 23.82, 25.61, 27.33, 28.37, 29.50, 51.04,106.56, 117.18, 124.28, 126.00, 126.43, 127.45, 130.01, 132.70, 134.00,139.11, 139.20, 150.23; MS m/z 343 (Mþþ1); HRMS: (EI, 70 eV) calcdfor C24H26N2 342.20960 (Mþ) found for m/z 342.20941.

The crystal data of 3d: C30H31N3, M¼433.58, triclinic, P-1,a¼10.219(6) Å,b¼11.256(9) Å, c¼11.618(7) Å, a¼65.78(7) �,b¼81.96(6) �, g¼81.30(5)�, V¼1200.2(14) Å3, Z¼2, Dc¼1.200 gcm�3,m (Mo-Ka)¼0.071 mm�1, F(000)¼464, rectangular block, colorless,size¼0.175�0.125�0.075 mm, 4868 reflections measured(Rint¼0.0414), 4109 unique, wR2¼0.2061 for all data, conventionalR¼0.0674 [(D/s)max¼000] on F-values of 1525 reflections withI>2s(I), S¼0.928 for all data and 299 parameters (deposit No: 3d:759528).

4 . 2 . 2 . 6 - ( 4 - M e t h yl p i p e r i d i n - 1 - y l ) - 1, 2 , 3 , 4 , 7 , 8 - h e x a hy -drobenzo[c]phenanthrene-5-carbonitrile (3b). White powder; yield:92%; mp: 150–152 �C; IR (KBr): 2951, 2371, 2215, 1596, 1430, 1382,1352, 1283, 1116, 1028 cm�1; 1H NMR (300 MHz, CDCl3): d 1.0 (d,J¼6.12 Hz, 3H, CH3), 1.41–1.44 (m, 2H, CH2), 1.56–1.57 (m, 1H, CH),1.61–1.40 (m, 4H, CH2),1.84–1.93 (m, 2H, CH2), 2.66 (d, J¼6.09 Hz, 2H,CH2), 2.72 (br s, 2H, CH2), 2.93 (t, J¼5.95 Hz, 2H, CH2), 3.01 (t,J¼6.80 Hz, 2H, CH2), 3.22 (br s, 2H, CH2), 3.33 (br s, 2H, CH2), 7.22–7.31(m, 3H, ArH), 7.55–7.59 (m,1H, ArH); MS m/z 357 (Mþþ1); HRMS: (EI,70 eV) calcd for C25H28N2 356.22525 (Mþ) found for m/z 356.22541.

4.2 .3 . 6-(4-Benzylpiperidin-1-yl)-1,2 ,3 ,4 ,7,8-hexahydro-benzo[c]phenanthrene-5-carbonitrile (3c). White powder; Yield:87%; mp: 148–150 �C; IR (KBr): 2820, 2378, 2203, 1605, 1434, 1384,1352, 1197, 1140 cm�1; 1H NMR (300 MHz, CDCl3): d 1.45–1.47 (m,2H, CH2), 1.61–1.72 (m, 5H, CH and CH2), 1.83–1.92 (m, 2H, CH2),2.60–2.66 (m, 4H, CH2), 2.72 (br s, 2H, CH2), 2.92 (t, J¼5.89 Hz, 2H,CH2), 3.0 (t, J¼6.75 Hz, 2H, CH2), 3.12 (br s, 2H, CH2), 3.30 (br s, 2H,CH2), 7.16–7.20 (m, 3H, ArH), 7.23–7.31 (m, 5H, ArH), 7.54–7.57 (m,1H, ArH); 13C NMR (75 MHz, CDCl3): 21.33, 21.99, 27.32, 28.37,29.48, 31.96, 36.64, 42.15, 50.28, 75.98, 117.09, 124.31, 124.56,126.01, 126.47, 126.94, 127.47, 127.87, 130.19, 132.67, 134.04, 139.18,139.36, 149.86; MS m/z 433 (Mþþ1); HRMS: (EI, 70 eV) calcd forC31H32N2 432.25655 (Mþ) found for m/z 432.25617.

4 . 2 . 4 . 6 - ( 4 - B e n z yl p i p e ra z i n - 1 - y l ) - 1, 2 , 3 , 4 , 7 , 8 - h e x a h y -drobenzo[c]phenanthrene-5-carbonitrile (3d). White powder; yield:95%; mp: 154–156 �C; IR (KBr): 2931, 2363, 2214, 1595, 1436, 1351,

1208, 1136, 1006 cm�1; 1H NMR (300 MHz, CDCl3): d 1.62 (m, 2H,CH2), 1.84–1.93 (m, 2H, CH2), 2.62–2.67 (m, 6H, CH2), 2.72–2.74 (m,2H, CH2), 2.93 (t, J¼5.94 Hz, 2H, CH2), 3.01 (t, J¼6.78 Hz, 2H, CH2),3.29 (br s, 4H, CH2), 3.58 (s, 2H, CH2), 7.24–7.39 (m, 8H, ArH), 7.54–7.57 (m, 1H, ArH); 13C NMR (75 MHz, CDCl3): 21.11, 21.97, 24.13,27.39, 28.28, 29.50, 49.63, 52.78, 62.02,107.23,116.91,124.35,125.77,126.01, 126.53, 126.97, 127.47, 127.94, 130.51, 132.54, 133.92, 137.06,139.07, 139.18, 139.31, 148.86; MS m/z 434 (Mþþ1); HRMS: (EI,70 eV) calcd for C30H31N3 433.25180 (Mþ) found for m/z 433.25200.

4.3. General procedure for the synthesis of 6-sec-amino-1,2,7,8-tetrahydrobenzo[c]phenanthrene (3e–g)

These were prepared from the reaction of 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles and 2-cyclo-hexenone and work-up as described in the earlier experiment. Thecrude product was purified by neutral alumina column using 4%ethyl acetate in hexane as eluent.

4.3.1. 6-(Piperidin-1-yl)-1,2,7,8-tetrahydrobenzo[c]phenanthrene-5-carbonitrile(3e). White powder; yield: 79%; mp: 162–164 �C; IR(KBr): 2957, 2362, 2203, 1584, 1417, 1352, 1300, 1209, 1105 cm�1; 1HNMR (300 MHz, CDCl3): d 1.64–1.72 (m, 6H, CH2), 2.32–2.39 (m, 2H,CH2), 2.67–2.72 (m, 2H, CH2), 2.74–2.79 (m, 2H, CH2), 3.01 (t,J¼8.05 Hz, 2H, CH2), 3.22 (br s, 3H, CH2 and CH), 3.90 (br s, 1H, CH),6.09–6.15 (m, 1H, CH), 6.77–6.81 (m, 1H, CH), 7.25–7.29 (m, 3H,ArH), 7.48–7.50 (m, 1H, ArH); 13C NMR (50 MHz, CDCl3): 21.75,24.22, 24.86, 26.85, 27.01, 29.38, 52.26, 52.82, 118.34, 124.76, 125.80,126.60, 127.29, 127.58, 127.89, 129.50, 133.28, 135.50, 137.52, 139.93,140.81, 151.32; MS m/z 341 (Mþþ1); HRMS: (EI, 70 eV) calcd forC24H24N2 340.19395 (Mþ) found for m/z 340.19403.

4.3.2. 6-(4-Methylpiperidin-1-yl)-1,2,7,8-tetrahydrobenzo[c]phenan-threne-5-carbonitrile (3f). White powder; yield: 84%; mp: 130–132 �C; IR (KBr): 3018, 2934, 2363, 2222, 1655, 1560, 1429, 1217,1009 cm�1; 1H NMR (300 MHz, CDCl3): d 1.01 (d, J¼4.77 Hz, 3H,CH3), 1.28–1.42 (m, 2H, CH2), 1.55–1.62 (m, 1H, CH), 1.69 (d,J¼11.61 Hz, 2H, CH2), 2.31–2.39 (m, 2H, CH2), 2.71 (br s, 4H, CH2),3.01 (t, J¼8.05 Hz, 2H, CH2), 3.13 (br s, 2H, CH2), 3.34 (br s, 2H, CH2),6.08–6.15 (m, 1H, CH), 6.77–6.81 (m, 1H, CH), 7.24–7.29 (m, 3H,ArH), 7.47–7.50 (m, 1H, ArH); 13C NMR (75 MHz, CDCl3): 20.50,20.93, 25.76, 28.13, 28.42, 29.42, 33.93, 50.31, 124.55, 125.35,125.70, 126.04, 126.31, 126.65, 128.25, 132.03, 134.20, 136.28,138.68, 139.52, 149.90; MS m/z 355 (Mþþ1); HRMS: (EI, 70 eV)calcd for C25H26N2 354.20960 (Mþ) found for m/z 354.20911.

4.3.3. 6-(4-Benzylpiperazin-1-yl)-1,2,7,8-tetrahydrobenzo[c]phenan-threne-5-carbonitrile (3g). White powder; yield: 87%; mp: 164–166 �C; IR (KBr): 2935, 2365, 2204, 1597, 1478, 1384, 1351, 1248,1201 cm�1; 1H NMR (300 MHz, CDCl3): d 2.32–2.39 (m, 2H, CH2),2.62 (br s, 4H, CH2), 2.67–2.78 (m, 4H, CH2), 3.01 (t, J¼8.04 Hz, 2H,CH2), 3.31 (br s, 4H, CH2), 3.59 (s, 2H, CH2), 6.11–6.16 (m, 1H, CH),6.77–6.81 (m, 1H, CH), 7.24–7.39 (m, 8H, ArH), 7.47–7.49 (m, 1H,ArH); 13C NMR (75 MHz, CDCl3): 20.48, 23.86, 25.79, 28.05, 49.59,52.75, 62.0, 116.81, 124.61, 125.28, 125.78, 126.05, 126.63, 126.74,126.97, 127.93, 128.27, 131.87, 134.24, 138.56; MS m/z 432 (Mþþ1);HRMS: (EI, 70 eV) calcd for C30H29N3 431.23615 (Mþ) found for m/z431.23635.

4.4. General procedure for the synthesis of protected5-cyano-6-sec-amino-1,2,3,4,7,8-hexahydro-2-oxobenzo[c]phenanthrene (6)

These were obtained by stirring an equimolar mixture of 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles,cyclohexan-1,4-dionemonoalkyleneketal and KOH in DMF for

R. Pratap et al. / Tetrahedron 66 (2010) 1458–1464 1463

1–2 h. After completion of reaction, excess of DMF was removedunder reduced pressure. The reaction mixture was poured ontocrushed ice with vigorous stirring. Neutralization with 10% HCl gavea precipitate, which was filtered, washed with water, dried andpurified on neutral alumina column using 3% ethyl acetate inhexane as eluent.

4 . 4 .1. 5 - C ya n o - 6 - ( p i p e r i d i n - 1 - y l ) - 1, 2 , 3 , 4 , 7 , 8 - h e x a hy -drobenzo[c]phenanthrene-2-one-ethylene ketal (6a). White pow-der; yield: 91%; mp: 216–218 �C; IR (KBr): 2941, 2363, 2210, 1607,1452, 1291, 1252, 1095 cm�1; 1H NMR (300 MHz, CDCl3): d 1.62–1.70 (m, 6H, CH2), 2.05 (t, J¼7.04 Hz, 2H, CH2) 2.63–2.67 (m, 2H,CH2), 2.71–2.74 (m, 2H, CH2), 3.16 (s, 2H, CH2), 3.21 (t, J¼6.94 Hz,6H, CH2), 3.87–3.92 (m, 2H, CH2), 3.94–3.99 (m, 2H, CH2), 7.22–7.30(m, 3H, ArH), 7.49–7.52 (m, 1H, ArH); 13C NMR (75 MHz, CDCl3):d 22.97, 23.88, 25.57, 26.60, 28.24, 29.65, 38.47, 51.01, 63.33, 106.33,106.03, 106.96, 117.03, 124.53, 126.08, 126.40, 126.59, 127.07, 132.36,134.77, 137.48, 139.30, 139.48, 150.80; MS m/z 401 (Mþþ1); HRMS:(EI, 70 eV) calcd for C26H28N2O2 400.21508 (Mþ) found for m/z400.21493.

The crystal data of 6a: C26H28N2O2, M¼400.50, monoclinic, P 2(1)/n, a¼12.452(1) Å,b¼9.378(2) Å, c¼18.631(4) Å, b¼103.800(1) �,V¼2112.8(7) Å3, Z¼4, Dc¼1.259 gcm�3, m (Mo-Ka)¼0.080 mm�1,F(000)¼856, rectangular block, yellow, size¼0.25�0.175�0.125 mm,4843 reflections measured (Rint¼0.0387), 3723 unique, wR2¼0.1564for all data, conventional R¼0.0527 [(D/s)max¼000] on F-values of1534 reflections with I>2s(I), S¼0.964 for all data and 272parameters.

Unit cell determination and intensity data collection (2q¼50�)was performed on a Bruker P4 diffractometer at 293(2) K. Structuresolutions by direct methods and refinements by full-matrix least-squares methods on F2. Programs: XSCANS [Siemens AnalyticalX-ray Instrument Inc.: Madison, Wisconsin, USA 1996], SHELXTL-NT [Bruker AXS Inc.: Madison, Wisconsin, USA 1997], MERCURY[Version 1.4.1, Cambridge Crystallographic Data Center, 12 UnionRoad, Cambridge, CB2 1EZ, U. K]. CCDC (deposit No: 6a: 759529)contains the supplementary crystallographic data. These data canbe obtained free of charge from www.ccdc.cam.uk/conts/retrie-ving.html [or from the Cambridge Crystallographic Data Center, 12Union Road, Cambridge, CB2 1EZ, U. K; Fax: (internat.) þ44 1223/336 033; E-mail: deposit@ccdc.cam.ac.uk.

4.4.2. 5-Cyano-6-(4-methylpiperidin-1-yl)-1,2,3,4,7,8-hexahy-drobenzo[c]phenanthrene-2-one-ethylene ketal (6b). White pow-der; yield: 94%; mp: 220–222 �C; IR (KBr): 2919, 2362, 2208, 1592,1522, 1477, 1351, 1194 cm�1; 1H NMR (300 MHz, CDCl3): d 1.0 (d,J¼6.21 Hz, 3H, CH3), 1.34–1.41 (m, 2H, CH2), 1.50–1.55 (m, 1H, CH),1.68 (d, J¼11.82 Hz, 2H, CH2), 2.05 (t, J¼7.0 Hz, 2H, CH2), 2.65–2.71(m, 4H, CH2), 3.16–3.24 (m, 6H, CH2), 3.31 (br s, 2H, CH2), 3.87–3.92(m, 2H, CH2), 3.94–3.99 (m, 2H, CH2), 7.24–7.31 (m, 3H, ArH), 7.49–7.53 (m, 1H, ArH); 13C NMR (75 MHz, CDCl3): 20.90, 26.60, 28.24,29.41, 29.64, 33.94, 38.47, 50.30, 63.32, 106.96, 117.02, 124.53,126.07, 126.36, 126.58, 127.07, 132.37, 134.75, 137.48, 139.38, 150.63;MS m/z 415 (Mþþ1); HRMS: (EI, 70 eV) calcd for C27H30N2O2

414.23073 (Mþ) found for m/z 414.23091.

4.4.3. 5-Cyano-6-(4-benzylpiperidin-1-yl)-1,2,3,4,7,8-hexahy-drobenzo[c]phenanthrene-2-one-ethylene ketal (6c). White powder;yield: 89%; mp: 146–148 �C; IR (KBr): 2928, 2363, 2216, 1596, 1458,1354, 1119, 1060 cm�1; 1H NMR (300 MHz, CDCl3): d 1.45 (br s, 1H,CH), 1.60 (br s, 1H, CH), 1.70 (d, J¼10.38 Hz, 3H, CH and CH2), 2.05 (t,J¼7.04 Hz, 2H, CH2), 2.61 (d, J¼6.66 Hz, 2H, CH2), 2.65–2.70 (m, 4H,CH2), 3.16–3.24 (m, 8H, CH2), 3.87–3.92 (m, 2H, CH2), 3.94–3.96 (m,2H, CH2) 7.16–7.23 (m, 3H, ArH), 7.24–7.31 (m, 5H, ArH), 7.48–7.51(m, 1H, ArH); 13C NMR (75 MHz, CDCl3): 26.61, 28.21, 29.61, 31.90,36.64, 38.49, 42.13, 50.26. 63.34, 106.93, 117.50, 124.56, 126.09,

126.62, 126.93, 127.08, 127.86, 132.31, 134.80, 137.49, 139.31, 150.45;MS m/z 491 (Mþþ1); HRMS: (EI, 70 eV) calcd for C33H34N2O2

490.26203 (Mþ) found for m/z 490.26213.

4.4.4. 5-Cyano-6-(4-benzylpiperazin-1-yl)-1,2,3,4,7,8-hexahy-drobenzo[c]phenanthrene-2-one-ethylene ketal (6d). White pow-der; yield: 81%; mp: 180–182 �C; IR (KBr): 2923, 2373, 2210, 1595,1438, 1378, 1352, 1279, 1127 cm�1; 1H NMR (300 MHz, CDCl3):d 2.05 (t, J¼7.02 Hz, 2H, CH2), 2.61–2.66 (m, 6H, CH2), 2.71–2.73 (m,2H, CH2), 3.16 (s, 2H, CH2), 3.21 (t, J¼7.05 Hz, 2H, CH2), 3.28 (br s,4H, CH2), 3.58 (s, 2H, CH2), 3.87–3.92 (m, 2H, CH2), 3.93–3.99 (m,2H, CH2), 7.22–7.38 (m, 8H, ArH), 7.48–7.51 (m, 1H, ArH); 13C NMR(75 MHz, CDCl3): 24.16, 26.66, 28.15, 28.42, 29.61, 38.50, 49.59,52.73, 61.99, 63.34, 106.70, 106.91, 116.76, 124.60, 125.79, 126.10,126.69, 126.96, 127.10, 127.93, 132.19, 134.69, 136.98, 137.67, 139.18,139.49, 149.43; MS m/z 492 (Mþþ1); HRMS: (EI, 70 eV) calcd forC32H33N3O2 491.25728 (Mþ) found for m/z 491.25709.

4 . 4 . 5 . 5 - C ya n o - 6 - ( p i p e r i d i n - 1 - y l ) - 1, 2 , 3 , 4 , 7 , 8 - h e x a hy -drobenzo[c]phenanthrene-2-one-(2,2-dimethyltrimethylene)ketal(6e). White powder; yield: 94%; mp: 238–240 �C; IR (KBr): 2944,2849, 2205, 1594, 1437, 1354, 1277, 1114, 1089 cm�1; 1H NMR(300 MHz, CDCl3): d 0.83 (s, 3H, CH3), 1.03 (s, 3H, CH3), 1.65–1.70 (m,6H, CH2), 2.28 (t, J¼6.72 Hz, 2H, CH2), 2.64–2.74 (m, 4H, CH2), 3.08 (t,J¼6.93 Hz, 2H, CH2), 3.21–3.24 (m, 6H, CH2), 3.37 (d, J¼11.58 Hz, 2H,CH2), 3.63 (d, J¼11.49 Hz, 2H, CH2), 7.23–7.31 (m, 3H, ArH), 7.52–7.57(m, 1H, ArH); 13C NMR (75 MHz, CDCl3): 21.00, 21.56, 22.96, 23.84,24.0, 25.57, 25.76, 28.23, 28.90, 39.43, 51.0, 69.19, 96.33, 105.86,117.13, 124.61, 125.78, 126.06, 126.57, 127.11, 132.37, 134.75, 137.72,139.26, 139.44, 150.62; MS m/z 443 (Mþþ1); HRMS: (EI, 70 eV) calcdfor C29H34N2O2 442.26203 (Mþ) found for m/z 442.26188.

4.4.6. 5-Cyano-6-(4-benzylpiperidin-1-yl)-1,2,3,4,7,8-hexahy-drobenzo[c]phenanthrene-2-one-(2,2-dimethyltrimethylene)ketal(6f). White powder; yield: 89%; mp: 230–232 �C; IR (KBr): 3031,2861, 2219, 1253, 1209, 1156, 1021, 1000, 954, 761 cm�1; 1H NMR(300 MHz, CDCl3): d 0.83 (s, 3H, CH3), 0.97 (s, 3H, CH3), 1.02 (d,J¼4.81 Hz, 3H, CH3), 1.29–1.47 (m, 2H, CH2), 1.50–1.61 (m, 1H, CH),1.68 (d, J¼11.70 Hz, 2H, CH2), 2.27 (t, J¼6.78 Hz, 2H, CH2), 2.67–2.70(m, 4H, CH2), 3.08 (t, J¼6.84 Hz, 4H, CH2), 3.23 (s, 2H, CH2), 3.31 (brs, 2H, CH2), 3.37 (d, J¼11.22 Hz, 2H, CH2), 3.63 (d, J¼11.49 Hz, 2H,CH2), 7.22–7.30 (m, 3H, ArH), 7.52–7.55 (m, 1H, ArH); 13C NMR(75 MHz, CDCl3): 20.90, 21.01, 21.56, 24.12, 25.77, 28.24, 28.89,29.41, 33.95, 39.36, 50.29, 69.19, 96.35, 117.09, 124.60, 125.81,126.06, 126.56, 127.12, 132.39, 134.75, 137.78, 139.25, 139.44, 150.41;MS m/z 533 (Mþþ1); HRMS: (EI, 70 eV) calcd for C30H36N2O2

456.27768 (Mþ) found for m/z 456.27770.

4.4.7. 5-Cyano-6-(4-benzylpiperidin-1-yl)-1,2,3,4,7,8-hexahy-drobenzo[c]phenanthrene-2-one-(2,2-dimethyltrimethylene)ketal(6g). White powder; yield: 91%; mp: 182–184 �C; IR (KBr): 2949,2872, 2371, 2215, 1596, 1429, 1283, 1209, 1116, 1068, 1029, 936,749 cm�1; 1H NMR (300 MHz, CDCl3): d 0.83 (s, 3H, CH3), 1.02 (s, 3H,CH3), 1.42–1.45 (m, 1H, CH), 1.56 (s, 2H, CH2), 1.70 (d, J¼10.53 Hz,3H, CH and CH2), 2.26 (t, J¼6.76 Hz, 2H, CH2), 2.61 (d, J¼6.66 Hz, 2H,CH2), 2.67 (br s, 4H, CH2), 3.07 (t, J¼6.84 Hz, 4H, CH2), 3.22 (br s, 4H,CH2), 3.36 (d, J¼11.46 Hz, 2H, CH2), 3.62 (d, J¼11.43 Hz, 2H, CH2),7.16–7.20 (m, 3H, ArH), 7.24–7.31 (m, 5H, ArH), 7.53–7.55 (m, 1H,ArH); 13C NMR (50 MHz, CDCl3): 22.21, 22.77, 25.20, 26.98, 29.42,30.09, 33.11, 37.84, 40.67, 43.33, 51.45, 70.34, 97.51, 118.23, 125.76,125.84, 127.29, 127.81, 128.13, 128.33, 127.05, 133.53, 135.97, 138.99,140.49, 140.64, 151.43; MS m/z 533 (Mþþ1); HRMS: (EI, 70 eV) calcdfor C36H40N2O2 532.30898 (Mþ) found for m/z 532.30909.

4.4.8. 5-Cyano-6-(tetrahydroisoquinolin-2-yl)-1,2,3,4,7,8-hexahy-drobenzo[c]phenanthrene-2-one-(2,2-dimethyltrimethylene)ketal

R. Pratap et al. / Tetrahedron 66 (2010) 1458–14641464

(6h). White powder; yield: 99%; mp: 170–172 �C; IR (KBr): 2820,2734, 2210, 1595, 1437, 1382, 1352 cm�1; 1H NMR (300 MHz,CDCl3): d 0.84 (s, 3H, CH3), 1.03 (s, 3H, CH3), 1.55 (s, 2H, CH2), 2.30(br s, 2H, CH2), 2.62 (t, J¼6.30 Hz, 2H, CH2), 2.74 (br s, 2H, CH2),2.95–3.01 (m, 2H, CH2), 3.12 (t, J¼6.90 Hz, 2H, CH2), 3.27 (s, 2H,CH2), 3.39 (d, J¼11.52 Hz, 2H, CH2), 3.64 (d, J¼11.52 Hz, 2H, CH2),4.35 (s, 2H, CH2), 7.0–7.03 (m, 1H, ArH), 7.13–7.18 (m, 3H, ArH), 7.24–7.29 (m, 3H, ArH), 7.56–7.60 (m, 1H, ArH); 13C NMR (50 MHz,CDCl3): d 22.15, 22.71, 24.82, 25.14, 26.94, 29.24, 30.03, 30.46, 40.64,48.66, 52.70, 70.32, 97.42, 107.56, 117.89, 125.50, 125.80, 125.97,127.32, 127.88, 127.93, 128.29, 129.08, 133.34, 134.43, 134.68, 136.50,139.28, 140.48, 140.76, 150.13; MS m/z 491 (Mþþ1); HRMS: (EI,70 eV) calcd for C33H34N2O2 490.26203 (Mþ) found for m/z490.26189.

4.5. General Procedure for the synthesis of 2-oxo-6-sec-amino-1,2,3,4,7,8-hexahydrobenzo[c]phenanthrene-3-carbonitriles (7)

These were obtain through deprotection of ketal by stirring in80% formic acid for 1 h at room temperature. After completion ofthe reaction, excess of formic acid was removed and reactionmixture was poured onto ice cold water. The precipitate obtainedwas filtered washed with water and purified by crystallization with1:1 chloroform and methanol.

4 . 5 .1. 2 - O x o - 6 - ( p i p e r i d i n - 1 - yl ) - 1, 2 , 3 , 4 , 7 , 8 - h e x a hy d ro -benzo[c]phenanthrene-5-carbonitrile (7a). White powder; yield:97%; mp: 198–200 �C; IR (KBr): 2926, 2821, 2372, 2213, 1716, 1595,1435, 1383, 1351, 1282, 1232, 1199, 1025 cm�1; 1H NMR (300 MHz,CDCl3): d 1.66–1.73 (m, 6H, CH2), 2.53 (t, J¼6.60, 2H, CH2), 2.68–2.70(m, 2H, CH2), 2.76–2.78 (m, 2H, CH2), 3.24 (br s, 4H, CH2), 3.36 (t,J¼6.60 Hz, 2H, CH2), 3.88 (s, 2H, CH2), 7.26–7.29 (m, 4H, ArH); 13CNMR (75 MHz, CDCl3): d 22.89, 23.85, 25.54, 25.76, 28.08, 35.24,43.27, 51.11, 105.18, 116.83, 124.31, 124.82, 126.28, 127.06, 127.28,131.52, 135.22, 138.95, 139.52, 150.66, 208.44; MS m/z 357 (Mþþ1);HRMS: (EI, 70 eV) calcd for C24H24N2O 356.18886 (Mþ) found form/z 356.18897.

4.5.2. 6-(4-Benzylpiperidin-1-yl)-2-oxo-1,2,3,4,7,8-hexahydro-benzo[c]phenanthrene-5-carbonitrile (7b). White powder; Yield:97%; mp: 140–142 �C; IR (KBr): 2927, 2826, 2365, 2214, 1718, 1594,1436, 1382, 1350, 1231, 1116, 1028 cm�1; 1H NMR (300 MHz, CDCl3):d 1.54–1.57 (m, 2H, CH2), 1.73 (d, J¼10.23 Hz, 3H, CH and CH2), 2.52

(t, J¼6.67 Hz, 2H, CH2), 2.63 (d, J¼6.66 Hz, 2H, CH2), 2.69 (d,J¼5.10 Hz, 2H, CH2), 2.74 (br s, 2H, CH2), 3.14–3.22 (m, 2H, CH2),3.35 (t, J¼6.63 Hz, 4H, CH2), 3.88 (s, 2H, CH2), 7.17–7.22 (m, 3H,ArH), 7.27–7.32 (m, 6H, ArH); 13C NMR (50 MHz, CDCl3): d 26.97,29.28, 33.09, 36.43, 37.81, 43.31, 44.50, 51.59, 125.70, 125.83, 126.06,127.52, 128.52, 128.18, 128.31, 128.51, 132.70, 140.03, 140.43, 140.78,151.51, 209.59; MS m/z 447 (Mþþ1); HRMS: (EI, 70 eV) calcd forC31H30N2O 446.23581 (Mþ) found for m/z 446.23564.

Acknowledgements

VJR, RP, RR thank CSIR, New Delhi for their financial assistance.They are also thankful to SAIF, CDRI, Lucknow for providing spec-troscopic data. VPG is thankful to CSIR and AICTE, New Delhi, Indiafor supporting this work through major research projects.

References and notes

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3. Lunde, G.; Bjorseth, A. Nature (London) 1977, 268, 518.4. (a) Wood, A. W.; Chang, R. L.; Levin, W.; Ryan, D. E.; Thomas, P. E.; Croisy-

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